Density is known to influence the performance power of some light duty (LD) vehicles through its influence on the injection process. Increasing fuel density increases mass of fuel injected where the injection technology meters fuel volumetrically. However increasing density also produces more black smoke and hydrocarbon emissions because it decreases the air/fuel ratio. For this reason the maximum fuel density permitted under the European Standard EN590 (2000) diesel specification was reduced from 860 to 845 kg/m3 in 2000. In Sweden it is already the case that the minimum density specification has been relaxed below 820 kg/m3 for Class 1 (Swedish Class 1 SwC1) and Class 2 environmentally adapted gasoils. Although the specification for SwC1 gasoil permits viscosity up to 4.0 mm2/s (40° C.), fuel samples tend to have a viscosity of 2.0 mm2/s or less.
There is a need to explore new environmentally acceptable ways to improve power performance in diesel fuels.
Generally traditional power performance high density fuels have been associated with a characteristic viscosity. An analysis of worldwide diesel fuels that have had density and viscosity measured in the last four years shows a trend to a characteristic viscosity with higher density, related by a linear trend:
density (kg/m3)=12*viscosity (mm2/s)+797. For this reason it has not been possible from available data to decouple the effects of density and viscosity and explore these independently of each other. It is difficult to change density and viscosity significantly by using standard refinery techniques or standard fuel components, and we have therefore devised a use of a special component blended into finished fuel to change the properties of blend density and blend viscosity.